On the Web Builder Zone (from DZone) Giorgio Sironi has posted a new article that talks about the different kinds of testing you can do on your application - both on the frontend and backend.

Automated testing supports your constant effort in design and refactoring, and besides that ensures that your application actually works in a reliable and repeatable way. [...] In this article I'll describe the different categories of testing, as applied to a Zend Framework 1 application, but this classification pertains to every web application based on object-oriented programming. Since this kind of applications is obviously PHP-based, PHPUnit will be the tool of choice along with some of its standard extensions.

He looks at five different types of testing you can do on your application:

Unit testing

Pragmatic unit testing

Functional testing

Integration testing

Acceptance testing

Not all of these can be done with PHPUnit on the backend, but they (mostly) have automated tools of their own like Selenium for frontend interface testing.